Conventionally, the electric power steering device having a motor as its source of driving power is known. For example, as disclosed in a patent document, JP 2013-153619 A (Patent document 1), an electric power steering device has a first inverter for applying a voltage to a first winding wire and a second inverter for applying a voltage to a second winding wire, and a voltage applied to the second finding wire is controlled based on a deviation of the electric currents (i.e., a difference between an electric current supplied to the first winding wire, and an electric current supplied to the second winding wire).
When, in such case, there are two or more systems of winding wires and/or inverters, heat generation state may be different from system to system, causing a system to overheat. However, no consideration is made in the patent document 1 regarding an unevenness of heat generation among plural systems.